Fix Exchange ping.

- Restart pings whenever the service restarts.
- Improve the PingParser to handle all possible responses.
- Do a better job of restarting after interrupt.
- Add a way to request a "ping only" sync.
- Tweak the POST timeout a bit.

Bug: 9596786
Change-Id: I0f1f5ec23c94f2e3851fa5decae404be76b540bb
5 files changed